Conventionally, frame signals such as SONET and OTN frames, so-called constant bit rate (CBR) signals, are transferred to another apparatus through a transmitting apparatus. FIG. 17 is a block diagram of an internal configuration of a conventional transmitting apparatus. An add/drop multiplexer (ADM), for example, is applicable as the transmitting apparatus.
A transmitting apparatus 1500 includes interface cards 1501 (1501a to 1501n) and an SW card 1502 therein. Each of the interface cards 1501 has a segmenting unit 1511a that segments a CBR signal, and a CBR signal restoring unit 1511b that restores the CBR signal from the segmented signal inversely to the segmenting unit 1511a. 
For example, a CBR signal input from a transmission path (line) to the interface card 1501a of the transmitting apparatus 1500 is divided into multiple segments by the segmenting unit 1511a of the interface card 1501a, band is expanded, and the segments are transferred to the SW card 1502. Paths in the SW card 1502 are switched through switching and reach the interface card 1501 corresponding to the switching (e.g., the CBR signal restoring unit 1511b of the interface card 1501n in the example depicted) (path A), and the segment-based signal is restored to the CBR signal and output to another transmission path as the CBR signal. Such a technique of dividing (e.g., cell-dividing) a CBR signal is disclosed in Japanese Laid-Open Patent Publication No. 2006-50075.
However, in the above conventional technology, an output phase of each segment is dependent on the input CBR signal and, if input and output rates are not integral multiples of each other and if the CBR signal has a deviation or data is input in an unbalanced manner (i.e., with data missing), the segment output phase fluctuates. To accommodate these situations, a circuit that absorbs fluctuations in the segment output phase is provided to increase the size of a buffer that temporarily stores CBR signals, etc.